The present invention relates to a system in a remote location which is capable of operating totally automatically to call to a central computer under varying operating conditions, and transfer callback data from the remote location to the central computer.
Current programming distribution systems for television and interactive television programming include provisions or distribution of pay-per-view programs. Ensuring that subscribers can order and are charged properly for viewing pay-per-view programs is a problem in such systems. This problem has two aspects. First, it should be easy for a subscriber to order a pay-per-view program, and second the subscriber must be properly charged when a pay-per-view program is ordered and viewed.
In a cable distribution system, the subscribers are in a restricted geographical location around the cable head end, and there are a relatively low number of subscribers to that head end, e.g. generally one town. In such systems, to order a pay-per-view program the subscriber calls the cable provider on the telephone and speaks to a cable provider employee. This employee, then arranges to have proper codes sent via the cable connection to that subscriber""s cable box to descramble the pay-per-view program that was ordered, and revert to scrambling that channel when the program is over. The fee for viewing that pay-per-view is added to the subscriber bill at the same time. Because of the geographical proximity and relatively low number of subscribers, the telephone order system is a workable solution in such systems.
However, in a satellite distribution system, the subscriber locations are disbursed over a very wide geographical area, e.g. an entire continent, and there are several orders of magnitude more customers in a satellite distribution system than in any single cable head end. Thus, a phone order system in not practical in a satellite distribution system. It has been proposed, therefore, that the satellite receiver at each subscriber location maintain in a memory a record of any pay-per-view programs viewed by the subscriber. The record of such programs, is reported to a central location via a telephone/modem link, a process termed callback.
Telephone/modem links between cooperating computers are very well known. However, in the case of a satellite receiver, the callback modem will not be a part of a computer system under control of a computer operator. Instead, the callback modem must operate totally automatically. Several problems exist when a telephone modem is used to call back information without operator control and/or intervention. Because a callback can occur automatically at a predetermined time, without any knowledge of what the subscriber is doing, the callback mechanism needs to ensure that such a callback can occur without interfering with what the subscriber is doing, and without causing interference with or degradation of the subscriber""s phone operation. This, in turn, has several aspects. First, the callback modem must release the telephone line whenever the subscriber wants access to the phone.
Second, the callback modem must be able to operate automatically with telephone central offices which may have abnormal interface behaviors. Some of the abnormal interfaces presented by central offices include: very short dial tones; pulse dial only; distorted dial tones; 60 Hz modulation on the dial tone; no dial tone; fast busy return tone; long delay before dial tone; fluctuation telephone line current during telephone access; and/or fluctuating current between off hook operation.
Third, the callback modem must be able to transfer the subscriber data through unknown distortions introduced by the telephone line connections between the callback modem and the central computer. Some distortions may be compensated by utilizing an adaptive equalizer, in a known manner. However, in some cases, the dynamic conditions of the telephone line, line loss conditions at the called modem location, and distortions presented. by the modem coupling transformer are not correctable using an adaptive equalizer.
EP 0 527 072 A2 issued to White et al. discloses a telephone dial-inbound data acquisition system with demand reading capability and U.S. Pat. No. 4,132,864 issued to Joseph S. Feng discloses a device for detecting a telephone off-hook situation.
The above mentioned problems must be addressed and overcome in a desired callback modem adapter for totally automatic operation.
In accordance with principles of the present invention, a subscriber callback modem includes a source of callback data. A modem is coupled to a subscriber telephone line, and a control circuit is coupled between the data source and the modem, for conditioning the modem to automatically call a central computer and transfer the callback data from the data source to the central computer